Tuesday's Tip - How to recognise a faulty ABS sensor.

An ABS sensor (often refered to as a wheel speed sensor or ESP sensor) is a photocell sensor located behind each wheel of the vehicle to detect when one the speed of one or more wheels varies from the rest, therefore triggering the ABS system to cut in and redistribute the brake force in order to prevent loss of control due to "skidding". These sensors can also be linked in with "traction control" or "electronic stabilitly program" systems which are fitted to many newer model vehicles to prevent wheel spin and loss of traction.

If an ABS sensor is faulty you will usually see one or more warning lights coming on, usually amber in colour these can read ABS or ESP or can have a symbol usually featuring a triangle with a car or an  exclamation mark in the centre. In most instances only one sensor will fail at a time, therefore the vehicle will need to be checked using computer diagnistic equipment to confirm which sensor requires replacement.

Replacement of the sensor on the majority of vehicles is a simple operation, most cars have the sensor fitted into the hub, taking its reading from an ABS ring around the bearing area. Once the faulty sensor is replaced most systems will reset themselves within a few miles without the need for the system to be reset.